In a conventional vapor compression cycle for use in a refrigeration or liquid chilling system, the refrigerant is compressed into a gas or vapor by the compressor and delivered to a condenser. The gas or vapor flow through the condenser where the heat of vaporization is removed, and it is changed to a liquid as it leaves the condenser, and it then expands through a throttle valve. As the refrigerant expands part of it flashes into vapor, and it enters the evaporator where the heat from flowing water or other liquid boils the refrigerant vapor. The actual operating cycle is somewhat less efficient than the theoretical cycle, partly because of pressure drop losses and partly because more power is used in compression. Furthermore, it is also well known that expanding the liquid through a throttle valve, or what is commonly referred to as an expansion valve, is an inefficient process because the available energy in the expanding liquid is not used to perform work.